Comment Re:Why? (Score 1) 49
Seriously? Basically all life on Earth as we know it (with the exception of stuff like chemosynthetic life) ultimately gets its energy from the sun. When I was a kid, they taught this stuff in kindergarten. All other things being equal (and subject to some other factors, but not ones that greatly invalidate this general rule) crop yields are directly proportional to the amount of light we get from the sun. Dim that enough to prevent global warming, and we can't feed ourselves any more without using a lot more cropland. Not to mention that most farms operate on incredibly thin margins as it is, so there's a mass wave of them going out of business, etc.
The greenhouse effect doesn't happen because we get too much sunlight, it happens because the atmosphere is basically transparent to most of the incoming light but, when it gets converted to IR, the atmosphere is opaque to that IR, so it absorbs it and warms and re-emits it back to the ground. The amount of light passing through the atmosphere is a completely different variable. Trying to fix global warming by tweaking a different variable that affects other things too is a very tricky proposition. It's like if the water pressure in a downstairs tap is too high, but it's fine on the third floor, so you put in a regulator at the water main and reduce the pressure for the whole house. Great, you just solved the downstairs water pressure problem, but you just created a low water pressure problem on those upstairs taps. Basically, you will have "fixed" the wrong problem. If we want an analogy that relates more directly to heat, let's say you have an electronics project that keeps overheating. So you "solve" the problem by reducing the amperage from the power source. With less power it doesn't heat up so mach. Problem solved, except of course that now for some strange reason the LED display isn't lighting up right and it keeps powering on, then abruptly powering off and back on again. Weird.
I didn't even go into weather. Dimming the sun on a global scale will have a massive effect on weather. I mean, that's the idea right? To affect climate, which will also affect weather. The problem is that it won't just magically be the same weather you would get without the greenhouse effect, the actual distribution of energy will be different. Among other problems will be severe droughts in various areas that will increase desertification. Basically, you'll break monsoon cycles in some areas, decrease the hydrologic cycle overall, etc. If you're shaking your head and confused about how some of the same bad stuff from global warming can happen even in a system that reduces overall warming, that's one of the reasons why many have been trying to emphasize that it's about climate change. All of the Earth's biospheres as well as human civilizations tend to rely on the status quo. Massively changing it on the short term is usually a catastrophe. Global warming does that, but so does global dimming. You can't just target one single variable (global average temperature) and if you keep that stable, you're golden.